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In an electrical power system, harmonics basically means the multiples of the current or voltage at the fundamental voltage frequency. Whenever you look at a waveform and it's not the usual sinewave shape you expect, that means there are harmonics involved.
What causes Harmonics? Well, AC signals can be divided into linear and nonlinear. The nonlinear systems draw power in short, sudden pulses, and these pulses mess up the waveforms of the current, causing distortion.
This distortion then creates harmonics which lead to power quality problems that affect the load and the distribution system. TVs and other electronic devices are examples of nonlinear load systems.
Now, let's talk about fundamental electrical harmonics. This is where the power starts from the generator. The frequency here is known as the fundamental frequency or the first harmonic frequency.
It could be either 50 Hz or 60 Hz, depending on the country. All electrical and electronic systems are designed to work well with this frequency.
When it comes to harmonics orders and complex waveforms:
This makes the second harmonic start in the reverse direction, meaning a negative sequence current flows in the electrical circuit. This current affects the induction motor by opposing the rotating magnetic field, resulting in lower mechanical torque than expected. This type of harmonic is also called the negative sequence.
- Third-order Harmonics: It has a frequency that is three times that of the fundamental harmonic, so 150 Hz. This is a really dangerous one. From the waveform, both the third and fundamental harmonics currents reach zero at the same time and get high at the same value but in opposite points.
This makes the harmonics create a zero-sequence current, increasing the neutral voltages in the power system. Increasing the neutral voltage makes the relay operate the circuit breaker. This is caused by the third harmonic current, which is also known as triplens.
- Fifth-order Harmonics: It has a frequency of 250 Hz and similar characteristics to the third-order harmonics but with a higher operating frequency.
Waveform Analysis shows that a complex waveform is made up of a combination of the harmonics and the fundamental waveform, each with its own phase angles and peak values.
Active Harmonic filters are highly effective in addressing and resolving the aforementioned harmonic issues. They are specifically designed to detect and counteract the negative impacts caused by harmonics, ensuring a more stable and clean power supply.
By actively filtering out the harmonic components, active power filters help to maintain the quality and integrity of the electrical system, minimizing the disturbances and potential damage that harmonics can bring. Their application is crucial in various industries and power systems to achieve optimal power performance and reliability.
If you want to know more about harmonics or have any other questions, please feel free to contact us:sales@yt-electric.com at any time. Our professional team will be dedicated to providing you with assistance.
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